1. Field of the Invention
This invention relates to conveyor systems for moving load bearing units, such as carts and pallets, along a path defined by the conveyor system. More particularly, the invention is directed to a device for interrupting the movement of load bearing units at preselected locations along the conveyor path.
2. Description of the Prior Art
Various stop mechanisms for use with conveyor systems are known. Examples of these known mechanisms are discussed in the following United States Patents.
U.S. Pat. No. 3,158,105 teaches a conveyor system having a stop mechanism for automatically disconnecting a rack or trolley from a conveyor chain. The trolley has a towing arm which is pivotally mounted at one of its ends to the trolley and has a latch plate at its other end. The stop mechanism includes an arm pivotally mounted to a floor plate at a pivot point for horizontal swinging movement about the pivot point toward and away from the conveyor chain. When the arm is in a position away from the chain the stop mechanism is in a trolley pass position, and when the arm is in a position toward the chain the stop mechanism is in a trolley stop position. The arm is moved toward the stop position by a solenoid and is moved toward the pass position by a spring. The solenoid is actuated by a person as the trolley moves into position at the stop mechanism.
U.S. Pat. No. 3,315,614 teaches a conveyor system wherein a series of carts are moved by a conveyor chain. The conveyor chain includes a plurality of spaced apart dogs. Each cart has a vertically movable tow pin at its front end. When the tow pin is in the lowered position it engages the dogs of the conveyor chains so that the cart moves with the conveyor chain. When the tow pin is in the raised position it is disengaged from the dogs so that the cart will not move with the conveyor chain. The tow pin has a crossbar attached thereto which contacts a cam mounted on the floor next to the conveyor chain to lift the tow pin out of engagement with the conveyor chain dogs. Each cart also has a cam affixed thereto projecting to the rear of the cart. As a following cart moves against a stopped cart, the rearwardly projecting cam of the stopped cart contacts the crossbar of the following cart raising the tow pin of the following cart out of engagement with the conveyor chain dogs, thus, also stopping the following cart.
U.S. Pat. No. 3,894,629 teaches a conveyor system having a first chain conveyor and a second chain conveyor transversely located relative to the first chain conveyor. The first chain conveyor has a plurality of pivotally mounted pallet pusher members located therealong for engaging downwardly projecting flanges of pallets for moving the pallets with the chain conveyor. A stop device is located at a predetermined location along the chain conveyor. The stop device includes a movable cam and arresting dogs actuated by a hydraulic cylinder. The hydraulic cylinder is activated to move the cam and arresting dogs between a pallet stop position and a pallet release position. When the stop device is in the pallet stop position, the cam contacts the pivotal pallet pusher member pivoting the pusher member out of engagement with the flanges of the pallets which move the arresting dogs into engagement with the flange of the pallet, thus, stopping the pallet. When the stop device is in the pallet release position, the cam allows the pallet pusher member to pivot into engagement with the flange of the pallet while moving the arresting dogs out of contact with the flange of the pallet, thus, causing the pallet to move with the conveyor chain.
U.S. Pat. No. 3,995,561 teaches a power-and-free conveyor system having a main conveyor track and an adjacent power conveyor chain. A plurality of carriers are mounted on the track. Each carrier has a pivotally mounted pusher dog. The power conveyor chain includes a plurality of projecting pusher dogs. When the pusher dog of a carrier is pivoted to an elevated position, a pusher dog on the power conveyor chain engages the pusher dog causing the carrier to move along the conveyor track as the power conveyor chain moves. When the pusher dog of a carrier is pivoted to a recessed position, the pusher dog will not engage the pusher dog, and, therefore, the carrier will not be moved by the power conveyor chain. The pusher dog of each carrier has a forwardly projecting arm, the movement of this arm causing the pusher dog to pivot between the elevated and recessed positions discussed above. In operation, when the projecting end of the actuating arm of a following carrier contacts the rear of a preceding stopped carrier, the pusher dog of the following carrier is caused to pivot to the recessed position disengaging from the pusher dog of the power chain conveyor, thus, causing the following carrier to also stop.
U.S. Pat. No. 4,287,829 teaches a power-and-free conveyor system having a power chain location above a rail. Carriers have wheels which ride on the rail. The front wheels are covered by fenders and the rear wheels are covered by fenders. A plurality of pusher dog support members are attached at spaced intervals to the power chain for movement therewith. Each pusher dog support member has a pivotally mounted pusher dog and a pivotally mounted cam mounted in front of and connected to the pusher dog through a link arrangement. When the pusher dog is in the lowered position it contacts the back side of the fender over the front wheels of the carrier, thus, moving the carrier with the power chain. When the pusher dog is in the raised position, it is out of contact with the front fender and the carrier is disengaged from the power chain. A stop device is located at a predetermined location along the power chain. The stop device includes a pivotally mounted lever which is caused to pivot into and out of engagement with the front fender of a carrier, by a hydraulic position. When the lever contacts the front fender of a carrier, the pivotally mounted pusher dog rides over the front fender of the carrier and the carrier is stopped. When a following carrier makes contact with the stopped carrier, the cam of the following carrier contacts the rear fender of the stopped carrier and pivots the pusher dog of the following carrier out of contact with the front fender of the following carrier causing the following carrier to also stop.
The aforementioned stop mechanisms are relatively complicated in construction and, therefore, difficult to manufacture and maintain in operation.